An extrusion die is known comprising a block and a flow-splitting and flow-displacement body mounted in the block. The block has an inlet, two feed passages communicating with the inlet and separated by the flow-displacing body, transversely widened gaps communicating with the passages and an outlet duct.
The flow-splitting and flow-displacement body has a mounting portion and a guide portion and is located downstream of the inlet duct. It separates both feed passages and both transversely widened gaps and projects with a sword-like piece or tongue of the guide portion into the outlet duct to form two outlet gaps. It terminates upstream of the mouth of the outlet duct to define therein an inner expansion chamber. It is understood that the block can have thermal insulation and/or temperature control means for heating or cooling the resin flow.
In practice the known extrusion die has transversely spaced ribs or webs bracing on the flow-splitting and flow-displacement body in the vicinity of the transversely broadened gaps to support it about which the thermoplastic material flows. The supporting ribs produce an undesirable texture in the products and damage the structure of the manufactured thermoplastic foam mats or plates which are frequently found to be unsatisfactory. The extruded structure made with such dies is frequently also impaired by non-uniform foaming also in the edge regions of the thermoplastic foam plate or thermoplastic foam mat.